author  paulson 
Fri, 30 Aug 2002 16:42:45 +0200  
changeset 13550  5a176b8dda84 
parent 13343  3b2b18c58d80 
child 13639  8ee6ea6627e1 
permissions  rwrr 
10358  1 
(* Title: HOL/Relation.thy 
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ID: $Id$ 
1983  3 
Author: Lawrence C Paulson, Cambridge University Computer Laboratory 
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Copyright 1996 University of Cambridge 

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*) 
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header {* Relations *} 
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theory Relation = Product_Type: 

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subsection {* Definitions *} 
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constdefs 
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converse :: "('a * 'b) set => ('b * 'a) set" ("(_^1)" [1000] 999) 
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"r^1 == {(y, x). (x, y) : r}" 

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syntax (xsymbols) 

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converse :: "('a * 'b) set => ('b * 'a) set" ("(_\<inverse>)" [1000] 999) 
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constdefs 
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rel_comp :: "[('b * 'c) set, ('a * 'b) set] => ('a * 'c) set" (infixr "O" 60) 
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"r O s == {(x,z). EX y. (x, y) : s & (y, z) : r}" 
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fun_rel_comp :: "['a => 'b, ('b * 'c) set] => ('a => 'c) set" 

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"fun_rel_comp f R == {g. ALL x. (f x, g x) : R}" 

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Image :: "[('a * 'b) set, 'a set] => 'b set" (infixl "``" 90) 
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"r `` s == {y. EX x:s. (x,y):r}" 
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Id :: "('a * 'a) set"  {* the identity relation *} 
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"Id == {p. EX x. p = (x,x)}" 
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diag :: "'a set => ('a * 'a) set"  {* diagonal: identity over a set *} 
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"diag A == UN x:A. {(x,x)}" 
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Domain :: "('a * 'b) set => 'a set" 
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"Domain r == {x. EX y. (x,y):r}" 
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Range :: "('a * 'b) set => 'b set" 
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"Range r == Domain(r^1)" 
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Field :: "('a * 'a) set => 'a set" 
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"Field r == Domain r Un Range r" 
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refl :: "['a set, ('a * 'a) set] => bool"  {* reflexivity over a set *} 
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"refl A r == r \<subseteq> A \<times> A & (ALL x: A. (x,x) : r)" 
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sym :: "('a * 'a) set => bool"  {* symmetry predicate *} 
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"sym r == ALL x y. (x,y): r > (y,x): r" 
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antisym:: "('a * 'a) set => bool"  {* antisymmetry predicate *} 
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"antisym r == ALL x y. (x,y):r > (y,x):r > x=y" 
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trans :: "('a * 'a) set => bool"  {* transitivity predicate *} 
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"trans r == (ALL x y z. (x,y):r > (y,z):r > (x,z):r)" 
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single_valued :: "('a * 'b) set => bool" 
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"single_valued r == ALL x y. (x,y):r > (ALL z. (x,z):r > y=z)" 
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inv_image :: "('b * 'b) set => ('a => 'b) => ('a * 'a) set" 
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"inv_image r f == {(x, y). (f x, f y) : r}" 
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syntax 
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reflexive :: "('a * 'a) set => bool"  {* reflexivity over a type *} 
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translations 
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"reflexive" == "refl UNIV" 
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subsection {* The identity relation *} 
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lemma IdI [intro]: "(a, a) : Id" 

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by (simp add: Id_def) 

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lemma IdE [elim!]: "p : Id ==> (!!x. p = (x, x) ==> P) ==> P" 

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by (unfold Id_def) (rules elim: CollectE) 

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lemma pair_in_Id_conv [iff]: "((a, b) : Id) = (a = b)" 

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by (unfold Id_def) blast 

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lemma reflexive_Id: "reflexive Id" 

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by (simp add: refl_def) 

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lemma antisym_Id: "antisym Id" 

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 {* A strange result, since @{text Id} is also symmetric. *} 

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by (simp add: antisym_def) 

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lemma trans_Id: "trans Id" 

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by (simp add: trans_def) 

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subsection {* Diagonal: identity over a set *} 
12905  91 

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lemma diag_eqI: "a = b ==> a : A ==> (a, b) : diag A" 

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by (simp add: diag_def) 

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lemma diagI [intro!]: "a : A ==> (a, a) : diag A" 

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by (rule diag_eqI) (rule refl) 

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lemma diagE [elim!]: 

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"c : diag A ==> (!!x. x : A ==> c = (x, x) ==> P) ==> P" 

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 {* The general elimination rule. *} 
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by (unfold diag_def) (rules elim!: UN_E singletonE) 
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lemma diag_iff: "((x, y) : diag A) = (x = y & x : A)" 

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by blast 

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lemma diag_subset_Times: "diag A \<subseteq> A \<times> A" 
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by blast 
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subsection {* Composition of two relations *} 

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lemma rel_compI [intro]: 
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"(a, b) : s ==> (b, c) : r ==> (a, c) : r O s" 
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by (unfold rel_comp_def) blast 

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lemma rel_compE [elim!]: "xz : r O s ==> 
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(!!x y z. xz = (x, z) ==> (x, y) : s ==> (y, z) : r ==> P) ==> P" 
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by (unfold rel_comp_def) (rules elim!: CollectE splitE exE conjE) 

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lemma rel_compEpair: 

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"(a, c) : r O s ==> (!!y. (a, y) : s ==> (y, c) : r ==> P) ==> P" 

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by (rules elim: rel_compE Pair_inject ssubst) 

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lemma R_O_Id [simp]: "R O Id = R" 

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by fast 

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lemma Id_O_R [simp]: "Id O R = R" 

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by fast 

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lemma O_assoc: "(R O S) O T = R O (S O T)" 

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by blast 

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lemma trans_O_subset: "trans r ==> r O r \<subseteq> r" 
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by (unfold trans_def) blast 
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lemma rel_comp_mono: "r' \<subseteq> r ==> s' \<subseteq> s ==> (r' O s') \<subseteq> (r O s)" 
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by blast 
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lemma rel_comp_subset_Sigma: 

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"s \<subseteq> A \<times> B ==> r \<subseteq> B \<times> C ==> (r O s) \<subseteq> A \<times> C" 
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by blast 
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subsection {* Composition of function and relation *} 

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lemma fun_rel_comp_mono: "A \<subseteq> B ==> fun_rel_comp f A \<subseteq> fun_rel_comp f B" 

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by (unfold fun_rel_comp_def) fast 

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lemma fun_rel_comp_unique: 
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"ALL x. EX! y. (f x, y) : R ==> EX! g. g : fun_rel_comp f R" 

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apply (unfold fun_rel_comp_def) 

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apply (rule_tac a = "%x. THE y. (f x, y) : R" in ex1I) 

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apply (fast dest!: theI') 

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apply (fast intro: ext the1_equality [symmetric]) 

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done 

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subsection {* Reflexivity *} 

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lemma reflI: "r \<subseteq> A \<times> A ==> (!!x. x : A ==> (x, x) : r) ==> refl A r" 

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by (unfold refl_def) (rules intro!: ballI) 
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lemma reflD: "refl A r ==> a : A ==> (a, a) : r" 

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by (unfold refl_def) blast 

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subsection {* Antisymmetry *} 

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lemma antisymI: 

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"(!!x y. (x, y) : r ==> (y, x) : r ==> x=y) ==> antisym r" 

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by (unfold antisym_def) rules 

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lemma antisymD: "antisym r ==> (a, b) : r ==> (b, a) : r ==> a = b" 

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by (unfold antisym_def) rules 

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subsection {* Transitivity *} 

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lemma transI: 

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"(!!x y z. (x, y) : r ==> (y, z) : r ==> (x, z) : r) ==> trans r" 

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by (unfold trans_def) rules 

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lemma transD: "trans r ==> (a, b) : r ==> (b, c) : r ==> (a, c) : r" 

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by (unfold trans_def) rules 

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subsection {* Converse *} 
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lemma converse_iff [iff]: "((a,b): r^1) = ((b,a) : r)" 

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by (simp add: converse_def) 
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lemma converseI[sym]: "(a, b) : r ==> (b, a) : r^1" 
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by (simp add: converse_def) 
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lemma converseD[sym]: "(a,b) : r^1 ==> (b, a) : r" 
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by (simp add: converse_def) 
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lemma converseE [elim!]: 

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"yx : r^1 ==> (!!x y. yx = (y, x) ==> (x, y) : r ==> P) ==> P" 

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 {* More general than @{text converseD}, as it ``splits'' the member of the relation. *} 
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by (unfold converse_def) (rules elim!: CollectE splitE bexE) 
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lemma converse_converse [simp]: "(r^1)^1 = r" 

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by (unfold converse_def) blast 

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lemma converse_rel_comp: "(r O s)^1 = s^1 O r^1" 

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by blast 

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lemma converse_Id [simp]: "Id^1 = Id" 

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by blast 

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lemma converse_diag [simp]: "(diag A)^1 = diag A" 
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by blast 
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lemma refl_converse: "refl A r ==> refl A (converse r)" 

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by (unfold refl_def) blast 

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lemma antisym_converse: "antisym (converse r) = antisym r" 

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by (unfold antisym_def) blast 

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lemma trans_converse: "trans (converse r) = trans r" 

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by (unfold trans_def) blast 

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subsection {* Domain *} 
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lemma Domain_iff: "(a : Domain r) = (EX y. (a, y) : r)" 

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by (unfold Domain_def) blast 

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lemma DomainI [intro]: "(a, b) : r ==> a : Domain r" 

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by (rules intro!: iffD2 [OF Domain_iff]) 

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lemma DomainE [elim!]: 

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"a : Domain r ==> (!!y. (a, y) : r ==> P) ==> P" 

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by (rules dest!: iffD1 [OF Domain_iff]) 

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lemma Domain_empty [simp]: "Domain {} = {}" 

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by blast 

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lemma Domain_insert: "Domain (insert (a, b) r) = insert a (Domain r)" 

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by blast 

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lemma Domain_Id [simp]: "Domain Id = UNIV" 

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by blast 

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lemma Domain_diag [simp]: "Domain (diag A) = A" 

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by blast 

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lemma Domain_Un_eq: "Domain(A Un B) = Domain(A) Un Domain(B)" 

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by blast 

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lemma Domain_Int_subset: "Domain(A Int B) \<subseteq> Domain(A) Int Domain(B)" 
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by blast 
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lemma Domain_Diff_subset: "Domain(A)  Domain(B) \<subseteq> Domain(A  B)" 
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by blast 
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lemma Domain_Union: "Domain (Union S) = (UN A:S. Domain A)" 

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by blast 

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lemma Domain_mono: "r \<subseteq> s ==> Domain r \<subseteq> Domain s" 
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by blast 
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subsection {* Range *} 

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lemma Range_iff: "(a : Range r) = (EX y. (y, a) : r)" 

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by (simp add: Domain_def Range_def) 

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lemma RangeI [intro]: "(a, b) : r ==> b : Range r" 

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by (unfold Range_def) (rules intro!: converseI DomainI) 

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lemma RangeE [elim!]: "b : Range r ==> (!!x. (x, b) : r ==> P) ==> P" 

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by (unfold Range_def) (rules elim!: DomainE dest!: converseD) 

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lemma Range_empty [simp]: "Range {} = {}" 

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by blast 

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lemma Range_insert: "Range (insert (a, b) r) = insert b (Range r)" 

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by blast 

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lemma Range_Id [simp]: "Range Id = UNIV" 

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by blast 

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lemma Range_diag [simp]: "Range (diag A) = A" 

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by auto 

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lemma Range_Un_eq: "Range(A Un B) = Range(A) Un Range(B)" 

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by blast 

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lemma Range_Int_subset: "Range(A Int B) \<subseteq> Range(A) Int Range(B)" 
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by blast 
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lemma Range_Diff_subset: "Range(A)  Range(B) \<subseteq> Range(A  B)" 
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by blast 
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lemma Range_Union: "Range (Union S) = (UN A:S. Range A)" 

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by blast 

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subsection {* Image of a set under a relation *} 

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lemma Image_iff: "(b : r``A) = (EX x:A. (x, b) : r)" 
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by (simp add: Image_def) 
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lemma Image_singleton: "r``{a} = {b. (a, b) : r}" 
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by (simp add: Image_def) 
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lemma Image_singleton_iff [iff]: "(b : r``{a}) = ((a, b) : r)" 
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by (rule Image_iff [THEN trans]) simp 
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lemma ImageI [intro]: "(a, b) : r ==> a : A ==> b : r``A" 
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by (unfold Image_def) blast 
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lemma ImageE [elim!]: 

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"b : r `` A ==> (!!x. (x, b) : r ==> x : A ==> P) ==> P" 
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by (unfold Image_def) (rules elim!: CollectE bexE) 
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lemma rev_ImageI: "a : A ==> (a, b) : r ==> b : r `` A" 

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 {* This version's more effective when we already have the required @{text a} *} 

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by blast 

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lemma Image_empty [simp]: "R``{} = {}" 

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by blast 

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lemma Image_Id [simp]: "Id `` A = A" 

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by blast 

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lemma Image_diag [simp]: "diag A `` B = A Int B" 

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by blast 

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lemma Image_Int_subset: "R `` (A Int B) \<subseteq> R `` A Int R `` B" 
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by blast 
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lemma Image_Un: "R `` (A Un B) = R `` A Un R `` B" 

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by blast 

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lemma Image_subset: "r \<subseteq> A \<times> B ==> r``C \<subseteq> B" 
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by (rules intro!: subsetI elim!: ImageE dest!: subsetD SigmaD2) 
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lemma Image_eq_UN: "r``B = (UN y: B. r``{y})" 

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 {* NOT suitable for rewriting *} 

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by blast 

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lemma Image_mono: "r' \<subseteq> r ==> A' \<subseteq> A ==> (r' `` A') \<subseteq> (r `` A)" 
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by blast 
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lemma Image_UN: "(r `` (UNION A B)) = (UN x:A.(r `` (B x)))" 

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by blast 

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lemma Image_INT_subset: "(r `` (INTER A B)) \<subseteq> (INT x:A.(r `` (B x)))" 
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 {* Converse inclusion fails *} 
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by blast 

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lemma Image_subset_eq: "(r``A \<subseteq> B) = (A \<subseteq>  ((r^1) `` (B)))" 
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by blast 
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subsection {* Single valued relations *} 
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lemma single_valuedI: 

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"ALL x y. (x,y):r > (ALL z. (x,z):r > y=z) ==> single_valued r" 
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by (unfold single_valued_def) 

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lemma single_valuedD: 

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"single_valued r ==> (x, y) : r ==> (x, z) : r ==> y = z" 

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by (simp add: single_valued_def) 

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subsection {* Graphs given by @{text Collect} *} 

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lemma Domain_Collect_split [simp]: "Domain{(x,y). P x y} = {x. EX y. P x y}" 

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by auto 

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lemma Range_Collect_split [simp]: "Range{(x,y). P x y} = {y. EX x. P x y}" 

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by auto 

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lemma Image_Collect_split [simp]: "{(x,y). P x y} `` A = {y. EX x:A. P x y}" 

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by auto 

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subsection {* Inverse image *} 
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lemma trans_inv_image: "trans r ==> trans (inv_image r f)" 
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apply (unfold trans_def inv_image_def) 
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apply (simp (no_asm)) 

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apply blast 

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done 

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end 